The switch current limit prevents the device from high inductor current and from drawing excessive current from the battery or input voltage rail. Excessive current can occur with a heavy load or shorted output circuit condition. If the inductor current reaches the threshold I_LIM, cycle by cycle, the high-side MOSFET is turned off and the low-side MOSFET is turned on until the inductor current ramps down to the low-side MOSFET current limit.

When the high-side MOSFET current limit is triggered 32 times, the device stops switching. The device then automatically re-starts with soft start after a typical delay time of 128μs has passed. The device repeats this mode until the high load condition disappears. This HICCUP short-circuit protection reduces the current consumed from the input supply during an overload condition. Figure 9-23 shows the hiccup short-circuit protection.

The HICCUP can be disabled by the CONTROL register bit Enable HICCUP. Disabling HICCUP changes the overcurrent protection to latching protection. The device stops switching after the high-side MOSFET current limit is triggered 32 times. Toggling the EN pin, removing and reapplying the input voltage, or writing to the CONTROL register bit Software Enable Device unlatches the device.

The low-side MOSFET also contains a negative current limit to prevent excessive current from flowing back through the inductor to the input. If the low-side sinking current limit is exceeded, the low-side MOSFET is turned off. In this scenario, both MOSFETs are off until the start of the next cycle. The negative current limit is only active in forced PWM mode.